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Unformatted text preview: Economic Statistics Exam 2 Name: June 5, 2009 PPID: Please sign that you abide by the honor pledge: This exam contains fifteen short answer questions ( worth 6 points each ) and three long answer questions ( worth 15 points each ) . Show your work clearly to be eligible for partial credit. In all problems where you need to make a calculation, simplify your answer as much as convenient. In questions with multiple parts, you should respond as if your answers to previous parts were correct. Short Questions ( 6 points apiece ) 1. What does the “central limit theorem” state? 2. My son is obsessed with the Pixar movie Cars . On the average day, he makes 4 requests to “watch Lightning McQueen, pease?” What is the chance that he makes more than 4 requests in a day? 3. Complete the following: When using a sample mean to construct a confidence interval for the mean of a normally distributed random variable, … … it is perfectly correct to use the z- distribution if … it is perfectly correct to use the t- distribution if … it is approximately correct to use the z- distribution if 4. A random variable X has a normal distribution with mean of 10 and variance of 4 . What is P [7 ! X ! 11] ? Econ 400 Midterm 2, page 2 of 7. 5. The mean weekly earnings of husbands in the U.S. in 2005 was $993 , with a standard deviation of $662 . The mean weekly earnings of wives was $604 , with a standard deviation of $454 . The correlation between spouses’ earnings is 0.42 . Find the mean and standard deviation of a married couple’s weekly earnings....
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